1. Field of the Invention
The present invention relates to primer compositions in non-flowable form. More particularly, the present invention relates to non-flowable primer compositions which are particularly useful for use with curable adhesive and sealant compositions in threadlocking, retaining, bonding and sealing applications and which can be packaged in a convenient pocket-sized applicator dispenser.
2. Brief Description of Related Technology
Liquid adhesive compositions have long been used in sealing, retaining, bonding and threadlocking applications and have become a standard part of assembly production as well as in the maintenance of machinery, tools and the like. Among the liquid adhesive compositions commonly used in these applications are anaerobic compositions. These single part compositions provide excellent threadlocking, retaining, bonding and sealant properties and remain stable until they are placed between parts where they cure in the absence of air. Moreover, these compositions remain stable for long periods of time during storage in the bottle.
In many applications, wicking of the liquid composition into tight spaces between adjoining parts is desirable. However, in many situations the ability of the liquid adhesive to migrate from parts is problematic, causing contamination of sensitive parts. Moreover, in many maintenance applications, the spillage of liquid adhesive compositions can be deleterious as well as inconvenient. One attempt to create a convenient ready-to-use threadlocking product has been the use of preapplied adhesive compositions, such as those in latex or micro-encapsulated form.
In such cases, the adhesive composition is applied to the threaded part, such as a bolt or nut, and remains in the uncured state until mated. As an example of a known preapplied adhesive composition, U.S. Pat. No. 4,497,916 discloses a continuous liquid phase adhesive composition to which is added solid wax-like particles dispersed therein. These particles may be chosen from polyethylene glycol materials having 4,000 to 20,000 molecular weight, stearic acid, acid waxes or stearic esters. The compositions disclosed in the '916 patent are formed by heating this combination of materials in slurry form and applying it, while heated, to threads. The composition then cools to obtain a non-mobile coating. This composition requires substantial preparation in order to obtain the composition and apply it on parts.
While preapplied coatings have many advantages, special processing is required to prepare and apply the adhesive coatings in advance. Such compositions are not useful on an as needed basis, such as when a immediate need for application of a curable composition is required. Moreover, to fully utilize preapplied compositions, it is necessary to stock and inventory of a variety of different sizes of threaded parts in advance. Thus, preapplied coatings do not solve the problem for many applications requiring ready-to-use compositions.
Attempts have been made to make a non-flowable anaerobic adhesive composition in the past. For example, U.S. Pat. No. 3,547,851 discloses anaerobic compositions which are rendered non-flowable at room temperature by uniform distribution throughout the adhesive of a network of normally solid organic substances insoluble in the adhesive. These organic substances are basically linear in nature and are typified by insoluble thermoplastic resins, such as solid paraffin hydrocarbons and normally solid fatty substances having about 10 or more carbon atoms. Efforts to date have failed in making a viable commercial product using the technology of this patent, due at least in part to the inability of the composition to maintain a non-flowable state at temperatures greater than room temperature. This has proved problematic, since warehouse temperatures often are greater than 100° F. (38° C.). Compositions made in accordance with the teachings of this patent have been limited by several technical difficulties. First, melting at elevated temperatures destroys the integrity of the composition and its ability to be applied. Furthermore, crumbling of these compositions during application or as a result of storage has been prevalent. Finally, the reductions in break torque due to the addition of the insoluble thermoplastic materials resulted in the inability to make a high strength composition. Relatively high levels of these insoluble thermoplastics were required to produce a non-flowable composition. Moreover, compositions of the '851 patent required melting of the insoluble thermoplastic materials prior to incorporation in adhesive. Heating or melting of the composition was required to get the desired effect of immobility.
As previously mentioned, the '851 patent discloses anaerobic compositions which have been rendered non-flowable through the inclusion of various waxes. The '851 patent, however, teaches away from using waxy materials having melting points greater than 250° F. (121° C.). Polyethylene glycol waxes, i.e., the preferred type of wax disclosed in the '851 patent, were found to melt during storage temperatures of about 130° F. (54° C.) and became brittle after extended periods of storage at normal temperatures.
Both the '851 and '916 patents discussed above require the addition of a solid material which is melted in order to be incorporated into the polymerizable monomer. Moreover, in practicing the '851 patent, an extremely large amount, e.g., 50% by weight, of polyethylene glycol was required in order to yield a composition which remained non-flowable at temperatures of about 158° F. (70° C.). Such extreme amounts of wax added to the polymerizable monomer significantly reduced the torque strength of threadlocking compositions.
In contrast, the present invention seeks to overcome such disadvantages and in particular addresses many of the specific deficiencies of the '851 patent, in the context of a primer composition, instead of an adhesive or sealant composition. The present invention provides a solution to creating non-flowable primer compositions, which can be stored at temperatures greater than about 100° F. (37° C.), such as about 120° F. (49° C.) up to about 160° F. (71° C.), without fear of loss of structural immobility through melting. Moreover, the present invention provides polymeric matrix additives which can be added directly to the primer composition without melting and which do not require heating or melting of the total combination in order to obtain the desired result.
The present invention seeks to obtain non-flowability at significantly greater temperatures, e.g., up to about 160° F. (71° C.) or more, while using as little as 2.5% to 20%, and desirably 7 to 10%, of the polymeric matrix. This is due to the unique physical and chemical properties of the polymeric matrix additive used in the present invention. Moreover, the present invention seeks to overcome the prior art problem of softening of the compositions over time.
Many commercial applications of curable compositions benefit from the use of a primer applied onto the substrate surface prior to application of the curable composition. See e.g. U.S. Pat. No. 5,811,473 (Ramos). In one such case, a primer composition has been described in a non-flowable form, by virtue of the use of the gelling agent, dibenzylidene sorbitol. See International Patent Publication No. WO 01/92345.
To date however it is not believed that a primer composition has been described or suggested that uses a primer compound, which can activate polymerization of a polymerizable composition; and a polymeric matrix selected from urea-urethanes, hydroxy or amine-modified aliphatic hydrocarbons, polyester-amide-based rheological additives and combinations thereof, to render the primer composition non-flowable at temperatures up to about 160° F. (71° C.) and where the primer composition is dispensable at room temperature without application of heat.